.textarea{
    width: 500px; 
    height: 200px; 
    border: 1px solid black;
    vertical-align: bottom;
}

.btn-send{
    padding: 10px;
    vertical-align: bottom;
}

.send-message,
.received-message{
    display: inline-block;
}

.iframe-page{
    width: 80%;
    height: 260px;
    margin: 10px;
    border: 10px solid green;
}